discussion on 2024-04-09

000
FXUS61 KOKX 091956
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
356 PM EDT Tue Apr 9 2024

.SYNOPSIS...
-- Changed Discussion --High pressure over eastern Canada builds south across the waters
east of New England through tonight. This will allow a dissipating
back door cold front to work across the area from the east this
evening into tonight. At the same time, a warm front approaching
form the west will become stationary just west of the area
tonight into Wednesday, then lifts north as a warm front on
Thursday as deepening low pressure draws closer over the Ohio
Valley. A cold front will move through early on Friday. As low
pressure departs the area, a secondary cold front swings through
early Saturday. High pressure then briefly noses in from the
south into Sunday. Another frontal system will potentially move
through on Monday.-- End Changed Discussion --

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
-- Changed Discussion --Upper level ridging between a closed low north of the Great
Lakes and another east of the Canadian Maritimes will translate
east across the area tonight. A confluent flow across eastern
Canada and the Northeast will also allow surface high pressure
to build south from Canada and across the waters east of New
England. The building high will send a dissipating back door
cold front west across the areas this evening into the first
half of tonight. At the same time, warm advection on the backside
of the ridge will send a warm front toward the area from the
west. The latter of which will stall before reaching the area.

Large scale warm advection will allow for increasing mid and
high level clouds to lower overnight. Rain chances will be low
with a slight chance rain toward daybreak for mainly NE NJ and
the Lower Hudson Valley. Plenty of dry air with low-level
ridging poking in from the east will take some time to saturate.

As for temperatures, with winds becoming easterly tonight at 10
mph or less and increasing clouds, opted to go warmer than the
MOS and NBM, leaned toward the CONSALL. This will keep lows 7
to 10 degrees above normal, in the lower 40s eastern sections,
to the mid and upper 40s NYC, NE NJ and the Lower Hudson Valley.-- End Changed Discussion --

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
-- Changed Discussion --Upper level ridge axis slips east of the area on Wednesday with
a low chance for some showers working from west to east across
the area during the day. Lift is weak and will combat a drier
airmass across eastern sections of the area. Rainfall amounts
will generally be less than a tenth of an inch. Stationary front
lifts north Wednesday night as an amplifying longwave trough
approaches works across the mid section of the country. Once
again though, rain chances will be low with any rainfall amounts
being light.

For temperatures, stayed below MOS and NBM by several degrees on
Wednesday due to the cloud cover and maritime airmass. Highs are
forecast to remain in the 50s, which is close to normal. For
Wednesday night, also went a bit warmer for the same reasons
with lows mid 40 to around 50.-- End Changed Discussion --

.LONG TERM /THURSDAY THROUGH TUESDAY/...
-- Changed Discussion --A surface low over the deep south on Wednesday will strengthen and
track into the eastern Great Lakes on Thursday in tandem with a
deepening upper-level trough to our west. This low will then
move to our north Friday.

A warm front ahead of the low will arrive Thursday morning and will
push north Thursday afternoon. Showers will develop with the warm
front aided by warm air advection and waves of mid-level energy
starting to arrive ahead of the low. Showers will become more
prevalent through the day as southerly flow increases,
advecting in more moisture from the Gulf stream. Peak moisture
with a strong LLJ will occur Thursday night into early Friday
morning with the latest 12Z guidance hinting at 1.3-1.6" PWATs.
This is at and above the max moving average of 1.36" for this
time of year according to SPC`s Sounding Climatology. This may
be further aided by a jet streak nearby placing us in the left
exit region during this same time frame. Its possible to have
periods of moderate to heavy rain overnight Thursday into early
Friday morning. The 13Z NBM currently gives a 30-40% chance for
at least 0.5" in 6 hours. Given the quick progression of the LLJ
and following cold front, the period of moderate to heavy
rainfall may not last long enough to meet flash flood guidance.
Only minor urban and poor drainage flooding is expected, along
with the potential for minor flooding at flashy small
streams/rivers. The areas of higher rainfall are likely to be in
the interior portions of our CWA in NY and CT. Currently
forecasting a large gradient of rainfall for the event with
southeastern portions of the CWA racking up 0.75" while
northwestern portions of the CWA total around 1.5".

A south-to-north oriented LLJ will start to build on Thursday,
reaching its peak of near 70 kt along coastal areas Thursday night
into Friday morning as it propagates west to east. Some models
have been bullish on surface winds speeds. Climatologically
speaking, colder waters in early Spring would lead to a stronger
inversion, thus preventing some of it from mixing down to the
surface. This is supported in model soundings showing a stronger
inversion. Currently forecasting peak gusts of 35-40 kts (40-45
mph) along Long Island and other southern coastal areas late
Thursday night into Friday morning.

Showers become scattered and lighter Friday afternoon, then taper
off Friday evening and Friday night as the low exits to the north
with a second cold front on Saturday. Winds will remain breezy until
Saturday morning as the pressure gradient weakens. A deeper trough
will center itself over the region during this time frame, becoming
zonal and weakening Saturday into Sunday. At the same time, high
pressure will briefly nose in from the south leading to dry
conditions Saturday night through most of Sunday. Model guidance
disagrees on Monday, but will likely see the trough to our north
begin to drop with some mid-level energy swinging in on Monday which
may provide a chance for scattered showers on Monday along with a
cold front.

High temperatures will be in the mid-60s to the west and in the mid-
50s to the east on Thursday with temperatures more uniform on
Friday near 60. Saturday will be cooler in the 50s due to a cold
front then warm into the mid-60s to mid-70s by Monday.-- End Changed Discussion --

.AVIATION /20Z TUESDAY THROUGH SUNDAY/...
VFR with high pressure into this evening.

S to SE sea breezes for most terminals this afternoon. Winds
mainly 10kt or less through the day. Winds then back more SE-E
tonight, remaining under 10kt. MVFR develops Weds morning with a
chance of -shra. Winds for Weds E-SE around 10kt.

NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...

Sea breeze shift to SE at KLGA may occur as early as 19z.

OUTLOOK FOR 18Z WEDNESDAY THROUGH SUNDAY...

Wednesday PM: Chance of showers. Mostly MVFR in the afternoon,
then mostly IFR at night.

Thursday: IFR with a chance of showers AM, then showers likely
with IFR/MVFR PM with SE gusts 20-25kt.

Thursday night: IFR and showers. SE gusts 30-35kt with LLWS.

Friday: IFR, S gusts 30-35kt, LLWS and showers AM. Chance of
showers PM with MVFR and SW gusts 30-35kt.

Saturday: Mainly VFR with a chance of MVFR in showers mainly NW
of the NYC metros. W-NW gusts 30-35kt.

Sunday: Mainly VFR. Chance of MVFR and showers in the
afternoon. SW-W gusts around 25 kt.

Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90

.MARINE...
-- Changed Discussion --A weak easterly flow across the waters through Wednesday night
will result in sub-SCA conditions.

As low pressure gets better organized to the west on Thursday and a
warm front lifts north expect a stronger south to southeast flow to
develop with small craft conditions becoming increasingly likely
later in the day.

Winds will be ramping up Thursday night with the approach of a
strong low pressure system. Southerly winds will peak late Thursday
night into Friday morning with sustained winds 30 to 35 kt and gusts
40 to 45 kt. Added a mention of gales to the HWO for this period.
Waves on the ocean waters peak Friday morning around 12 to 14 ft.
Waves on the LI Sound will also likely reach 5 to 7 ft, with the
higher waves close to the CT coast given the southerly flow.

Small Craft Advisories will likely linger on all waters through
Saturday as wind gusts remain around 25 kt. Sub SCA conditions then
expected thereafter, except on the ocean waters where 5 to 7 ft
waves could linger.-- End Changed Discussion --

.HYDROLOGY...
-- Changed Discussion --There are no hydrologic concerns through the day Thursday.

Its possible to have periods of moderate to heavy rain overnight
Thursday into early Friday morning. The 13Z NBM currently gives a 30-
40% chance for at least 0.5" in 6 hours. Given the quick progression
of the LLJ and following cold front, the period of moderate to heavy
rainfall may not last long enough to meet flash flood guidance. Only
minor urban and poor drainage flooding is expected, along with the
potential for minor flooding at flashy small streams/rivers. The
areas of higher rainfall are likely to be in the interior portions
of our CWA in NY and CT. Currently forecasting a large gradient of
rainfall for the event with southeastern portions of the CWA racking
up 0.75" while northwestern portions of the CWA total around 1.5".-- End Changed Discussion --

.TIDES/COASTAL FLOODING...
-- Changed Discussion --Astronomical high tides remain elevated with the new moon / spring
tide set up from early this week. Additional rounds of minor
flooding appear likely through mid to late week for the same
areas that experienced any coastal flooding from previous high
tide cycles, as tidal departures needed for minor drop as low as
1/4 ft thru Wed eve high tide. Localized pockets of moderate
coastal flooding remains a possibility for the western south
shore back bays.

Coastal Flood Advisories remain in effect for tonight`s high
tide cycle for coastal northeast NJ, southern Queens, southern
Nassau, southern Westchester and southern Fairfield. Up to 1 to
1.5 foot of inundation above ground level is expected in the
most vulnerable locations near the waterfront. Coastal Flood
Advisories have been issued elsewhere except the Bronx,
northeast Suffolk and southern New London.

Strengthening SE-S flow with a storm system late Thursday into
Friday morning may force more widespread minor to moderate coastal
flooding.-- End Changed Discussion --

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...Coastal Flood Advisory from 10 PM this evening to 2 AM EDT
Wednesday for CTZ009.
NY...Coastal Flood Advisory from 10 PM this evening to 2 AM EDT
Wednesday for NYZ071.
Coastal Flood Advisory from 7 PM this evening to 1 AM EDT
Wednesday for NYZ178-179.
NJ...Coastal Flood Advisory from 7 PM to 11 PM EDT this evening for
NJZ006-104-106-108.
MARINE...None.

SYNOPSIS...BR/DW
NEAR TERM...DW
SHORT TERM...DW
LONG TERM...BR
AVIATION...JC
MARINE...BR/DW
HYDROLOGY...BR/DW
TIDES/COASTAL FLOODING...//